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After installing 18x-LVC, the NTPClockOffset is in a much smaller range, from -10 to 25 microseconds:
GPSdiff is also much better behaved, ranging from a minimum of 0.5 to 1.1 seconds. The number of satellites tracked by the new GPS is also generally higher.
As expected, the frequency offset shows a temperature dependence in the oscillator. On a cool day in April, the
effect is not pronounced, and the frequency offset does not vary widely. The bottom trace shows a close relationship between the NTPClockOffset and the derivative of NTPFreqOffset, indicating how NTP adjusts the clock.
On a hot day in July, the relationship between NTPFreqOffset and the outside temperature is very pronounced.